The reaction of methanol and oxygen is known in the prior art. This reaction has been catalyzed by various catalytic species such as platinum, gold and palladium.
In U.S. Pat. No. 4,304,761 various oxidation routes for methanol are set forth including the reaction of methanol with oxygen to produce carbon dioxide and water. In that patent, experiments were conducted to arrive at a system for reducing methanol emissions from internal combustion exhaust gases. Large excesses of oxygen were utilized, wherein the oxygen to methanol ratio was 6.25, which is more than four times the stioichiometric requirement. Complete conversion of methanol requires temperatures of at least 125.degree. C. (257.degree. F.). At temperatures lower than the recited temperature, the methanol oxidized incompletely thus forming formaldehyde byproduct. The patent teaches that in order to get complete oxidation of methanol to carbon dioxide and water one should use stoichiometric excesses of oxygen and temperatures above 125.degree. C., well above ambient conditions. The catalysts demonstrated for activity included platinum, palladium, rhodium and silver.
In an article by Collin N. Hodges and Leonard C. Roselaar entitled Gold and Platinum Catalyzed Oxidation of Methanol appearing in the Journal of Applied Chemical Bio-Technology 1975 vol. 25 pages 609 to 614, the oxidation of methanol under oxygen deficient conditions (oxygen/methanol =0.5 mol fraction) using a platinum gauze catalyst was studied. The article indicates that the lowest reaction temperature of 150.degree. C. (302.degree. F.) resulted in the formation of formaldehyde. It required temperatures of 190 to 225.degree. C. (374 to 437.degree. F.) to produce a hydrogen or carbon dioxide product from methanol oxidation over a platinum catalyst. There is no suggestion in that article that lower temperatures, particularly temperatures approximating ambient, could result in complete conversion of oxygen and methanol.
In another article by J. G. Firth entitled Catalytic Oxidation of Methanol Over Platinum appearing in TransFaraday Society 1971 Volume 67 page 212, the oxidation of methanol was studied under conditions of excess oxygen (oxygen to methanol ratios of 2.5 up to 20) using a platinum catalyst. Some platinum catalyst activity was observed at ambient temperatures of 27.degree. C. (80.6.degree. F.), but at those temperatures methanol conversion was relatively low.
Carburization is a conventional method for case hardening of various ferrous articles, such as steel components. In the typical gas phase carburization technique, a gas atmosphere is utilized which has the capability of transferring carbon to the surface of the steel article being treated, such that the carbon is adsorbed onto the surface of the article and then diffused at appropriate temperatures into the surface zones of the article. Various carbon donating atmospheres have been used in the past including endothermic atmosphere produced from the combustion in a heated catalytic retort under partial oxidation conditions of a hydrocarbon with air to produce a mixture of carbon monoxide, hydrogen and nitrogen. Typically, endothermic atmospheres are produced external to the carburizing furnace and blended with additional hydrocarbon-enriching gas prior to entering the furnace.
It is also known to synthetically produce such an endothermic atmosphere within the carburizing furnace by blending methanol, nitrogen and a hydrocarbon and subjecting the mixture to high temperatures. It is theorized that the carbon monoxide acts as a shuttle for carbon from a high temperature heat source in the furnace to the surface of the ferrous article being treated. The source of the shuttled carbon is the enriching hydrocarbon gas. Such hydrocarbon is cracked under conditions of high temperature in the carburization furnace on the heat source or radiant tubes which are at a higher temperature than the articles being carburized. Water, present as a by-product in the carburization reactions, is believed to combine with the carbon cracked on the high temperature heating surfaces of the carburization furnace to form carbon monoxide and hydrogen. As the carbon monoxide contacts the ferrous articles to be carburized, the carbon monoxide reacts with hydrogen to deposit carbon on the article and result in water as a by-product. Therefore, the presence of carbon monoxide acts to shuttle the carbon of the cracking enriching gas from a high temperature surface in a carburizing furnace to the lower temperature surface of the articles being carburized, wherein the carbon monoxide disassociates to form carbon and oxygen, the latter of which reforms with available hydrogen to form water. It can be seen that in order to accelerate the carburizing effect, carbon monoxide must be readily available to shuttle carbon from the high temperature surface to the carburizing article. It is equally important to provide a carbon source consisting of the enriching gas in order to replenish the carbon utilized from carbon monoxide during the carburization and to allow the water of the carburizing reaction to reach the site of the cracking hydrocarbon so as to form carbon monoxide with such carbon.
This theory of carbon shuttling is set forth in an article by Kaspersma and Shay entitled "A Model For Carbon Transfer in Gas-Phase Carburization of Steel" presented in the Journal of Heat Treating, Vol. 1, No. 4, at page 27.
It is also known to utilize a methanol and enriching gas atmosphere without nitrogen in at least one stage of the carburization process as set forth in an article by Peartree entitled "Two-Step Accelerated Carburizing Shortens Cycle, Saves Energy" presented in Heat Treating, July 1981, page 36. The use of dissociated methanol and enriching gas undiluted with nitrogen in a continuous belt furnace is also discussed. The ratio of enriching gas to methanol was similar to that employed in a conventional carburizing furnace. Accelerated carburizing rates were observed with both techniques. The two-stage process set forth in the article wherein a pure methanolmethane atmosphere is initially used in one stage, while a synthetic endothermic atmosphere is used in a second stage of a carburization process is also the subject of U.S. Pat. No. 4,306,918.
In U.S. Pat. No. 4,317,687, a process for carburizing ferrous metal articles is set forth wherein nitrogen, ethanol and water are injected into the furnace with or without a hydrocarbon enriching agent, such as propane, to produce the carburizing atmosphere.
Patents of additional interest to the carburization art included U.S. Pat. No. 4,145,232 which is directed to a carburizing atmosphere in a furnace wherein the hydrocarbon is maintained in a precise concentration Z.sub.A below the level of 10% so as to minimize the amount of carburizing gas necessary, and U.S. Pat. No. 4,322,255 which is directed to a carburizing atmosphere wherein the atmosphere is measured in the carburizing furnace and the hydrocarbon content is controlled in the range of 0.2 to 30%.
U.S. Pat. No. 4,597,807 discloses using endothermic gases with a protective gas envelope of inert gas.
None of the above prior art suggests the viability of an ambient temperature feed to a reaction of stoichiometric excess quantities of methanol with oxygen content in a commercial inert gas stream, that effectively results in complete conversion of oxygen and methanol to beneficial byproducts of carbon monoxide, hydrogen, carbon dioxide and water without external heating. The present invention achieves such a result using appropriate catalyst to result in an efficient economical endothermic gas producing process as set forth below.